A patient often goes into shock when having a traumatic medical problem. When this happens, blood pressure drops rapidly and blood vessels tend to deflate or collapse all together. The importance of establishing access to the circulatory system through a blood vessel for volume control and administration of medication is second only to establishing the airway. In many cases, these steps are performed simultaneously.
It is also very important for a proper data base line on blood chemistry that blood samples be taken prior to administration of intravenous medication. However, in emergency situations, immediate attention must be devoted to revival or life sustaining measures. Lab work is either forgotten or time is not taken to acquire samples. Later a blood sample may become difficult to obtain since peripheral vessels may have collapsed, making a venipuncture impossible. Also, intravenous medications started earlier often render any later sample useless.
Intravenous administration of fluids is started with a flexible catheter slidably mounted over an elongated hypodermic needle. The needle adds rigidity to the otherwise flexible catheter. The needle hub may include a "flashback" chamber and vented plug (as shown in U.S. Pat. Nos. 4,269,186 and 4,193,400) to allow blood flow back through the needle and into the chamber, thereby indicating proper venipuncture. The needle hub and plug can be removed as the needle is withdrawn, after establishing "flashback", to allow mounting of a flexible supply tube to the catheter.
It is conventional today to take blood samples through a double ended needle assembly. One needle establishes venipuncture and delivers blood to second coaxial needle. The second needle is often covered by a rubber sleeve to stop free blood flow. A central hub between the needles is threaded for connection to a rigid container guide with the sleeve-covered second needle projecting into its interior. A rubber plugged specimen container may then be inserted into the guide and pressed against the second needle, which penetrates the sleeve and plug. The outer needle end is exposed to negative pressure within the container. Blood is thereby drawn through the inter-connected needles and into the specimen container. When enough blood has been drawn, the container is pulled free. The rubber sleeve again seals the needle. The rubber plug also closes to seal the container and blood specimen contained therein. The process can be repeated with successive specimen containers for as many specimens as required. This specimen gathering technique is effective, but must be performed as a separate function from intravenous catheterization.
Combining the functions of a specimen gathering needle and an intravenous catheterization has been previously attempted by using an intravenous catheterization set and a specially adapted syringe on the catheter needle hub. The catheter and needle are inserted in the usual manner. However, since there is no available "flashback" chamber, the only way to verify successful venipuncture is to aspirate the syringe. If there has been no venipuncture, no blood will appear in the syringe barrel and repositioning of the needle is necessary.
Combining conventional intravenous catheter sets having flashback chambers with an aspirator syringe at first glance appears to be a solution to the problem. However, in actual practice such a simple combination cannot function, since the syringe requires a hermetic seal between the syringe barrel and the patient's bloodstream. This conflicts with the necessity of the flashback chamber being vented to the atmosphere in order for the catheter set to properly function (see U.s. Pat. Nos. 4,269,186 and 4,193,400). The need remains today to safely and efficiently combine the function of an intravenous catheter and a blood specimen container system to gain the advantage of acquiring undiluted blood specimens without substantially interfering with or delaying application of intravenous fluids.